Abstract: The state of a file may be a combination of local state, typically small (e.g., a placeholder file), and some external source state such as that maintained in a read-only namespace managed by a cloud provider or by another local file system, typically large. A file system component responsible for overlaying (i.e., merging) the partial local state and the external source state into a single file system view that can be used by an application of a container as if the full state exists locally. Overlays that comprise the file system state may be referred to as “layers”. A tombstone mechanism may be provided to record delete or rename modifications in the top layer.